Electrodes have been implanted in the body for electrical cardioversion or pacing of the heart. More specifically, electrodes implanted in or about the heart have been used to reverse (i.e., defibrillate or cardiovert) certain life threatening arrhythmias, or to stimulate contraction (pacing) of the heart, where electrical energy is applied to the heart via the electrodes to return the heart to normal rhythm.
Cardiac pacing may be performed by the transvenous method or by electrodes implanted directly onto the epicardium. Transvenous pacing may be temporary or permanent. In temporary transvenous pacing an electrode catheter is introduced into a peripheral vein and fluoroscopically positioned against the endocardium. Traditional permanent transvenous pacing is performed under sterile surgical conditions where an electrode is positioned in the right ventricle or atrium through a subclavian vein, and the proximal terminals are attached to a pulse generator which is implanted subcutaneously. However, for certain conditions, for example, congestive heart failure or to improve hemodynamics, it can be more beneficial to couple the electrode with the left ventricle or the left atrium. This placement can provide stimulation of the left side only, or when used with a right sided lead can be used for biventricular pacing.
Lead placement within the left ventricle or left atrium, however, has been considered as involving more risk than lead placement within the right ventricle or right atrium since the left chambers involve pumping at higher pressures. In addition, the course of blood from the left ventricle to the body involves systemic circulation, where blood flows to several organs other than the lungs, such as the brain. Potential complications with blood clots which can be induced by the presence of the lead preclude lead implantation within left chambers of the heart. One approach to resolve this issue is to place the lead outside of the heart proximate the left ventricle or the left atrium. Traditionally, To attach a lead epicardially, a thoracotomy is performed where the thorax is opened to obtain access to the heart. This procedure involves painfuil and expensive surgery for the patient.
Accordingly, what is needed is a medical device for coupling with a portion of the heart. What is further needed is a lead which can be implanted within veins adjacent to the heart. What is also needed is a lead which minimizes drag during lead placement.